Extinction/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim looks up at a large skeleton of a dinosaur at a museum. TIM: Cool. {creaking} TIM: Whoa. Tim looks up toward the ceiling and sees Moby riding on a pterosaur, or a flying reptile skeleton suspended from the ceiling by wires. MOBY: Beep. TIM: Hey, get down from there! Moby extends his arm and hands Tim a letter. Tim reads from the typed letter. TIM: Dear Tim and Moby, how come there aren't dinosaurs anymore? From, Petra. About 65 million years ago, all of the dinosaurs on Earth went extinct. An image shows two dinosaurs fighting. TIM: Extinction happens when an entire species of animal dies out. An animation shows a tombstone that reads: R.I.P. Tyrannosaurus Rex. TIM: A species is any group of organisms that shares enough common traits to breed together. MOBY: Beep. TIM: Well, like you couldn't breed a cat and a dog. They're members of different species. Images show a cat and a dog. TIM: Anyway, there are millions of different species living on Earth today. Images show various species including fruit, flowers, animals, humans, bugs, and various plants. TIM: When people think about extinct animals, dinosaurs come to mind, the saber-tooth tiger, maybe the dodo bird. Side by side images show the animals Tim mentions. TIM: But extinction is a much bigger deal than a loss of a few really cool-looking creatures. More than 99 percent of all the species that ever lived on Earth are now gone, forever. That's over one billion extinct species! An animation shows a whole graveyard of tombstones reading R.I.P. to various extinct species including the Tyrannosaurus rex, passenger pigeon, and trilobite. MOBY: Beep. TIM: I know. Extinction can happen in several ways. Mass extinction occurs when a large percentage of all the species on Earth becomes extinct in a relatively short period of time. An animation shows tombstones for various dinosaurs popping up in the graveyard. TIM: Scientists believe that mass extinctions happen because of sudden environmental factors, like major changes in climate. An animation shows dinosaurs in a warm climate that suddenly turns snowy and icy. TIM: The loss of most of the dinosaurs was actually part of a mass extinction. It was likely the result of an environmental disaster caused at least partly by a meteor hitting the earth 65 million years ago. Three dinosaurs in a cold environment lie dead on the ground. TIM: Somewhere around half of all species on Earth died off when the dinosaurs did. Species can also go extinct from normal evolutionary pressure. A tombstone for the woolly mammoth pops up in the graveyard. TIM: Evolution is the process by which species change over many generations. An animation shows a tadpole changing into a fish, then changing into a lizard-like animal coming out of the water and onto land. MOBY: Beep. TIM: Yeah, it's called the theory of evolution, but in science, a theory is more than just a guess; it's a well-established model that's supported by repeated experimentation and hard evidence. So, according to the theory of evolution, all living things are constantly competing for resources like food, water, and space. When a type of organism loses out on these life essentials, its species eventually goes extinct. An animation shows a shellfish underwater. It looks a lot like a lobster, but has tiny claws. It grabs a piece of food. A lobster hits the creature over the head with its large claw and takes its food away with. The creature has no food and dies. MOBY: Beep. TIM: For most of Earth's history, somewhere between 10 and 100 species have gone extinct every year. The image of various species appears. Some of the species disappear and are replaced with tombstones. A timeline labeled 4.6 billion years marks a timespan. TIM: These days, that number has gone way up. Some biologists estimate that as many as 11 species on Earth go extinct every hour! The timeline is replaced by a clock. Its hands rotate one hour as species appearing above it are replaced with tombstones. MOBY: Beep. TIM: I don't mean to freak you out, but it is a big problem. Human activities like industry, farming, forestry, and commercial fishing put a lot of pressure on the environment. Animations and images illustrate the industries Tim describes. TIM: In the 1970s, the use of the pesticide DDT nearly drove the bald eagle to extinction in North America. An image shows a bald eagle. TIM: And when a species dies out, it can affect the entire ecosystem. MOBY: Beep. TIM: Well, think about food chains: If a plant species dies off, all the animals that eat it will have to scramble for different food, and some of them will die off, and then the animals that eat those smaller animals will be affected, too. An animation shows an insect eating a plant. A bird then eats that insect. TIM: It's important for us to remember that we share this planet. Humans depend on other life forms for all kinds of things, like food, clothing, medicine, and shelter, to name a few. Images show a chicken, a lamb, penicillin, and a tree. TIM: If we put too much pressure on the environment, we might drive the organisms we depend on to extinction. New tombstones pop up in the graveyard for Atlantic salmon, American chestnut and a grizzly bear. TIM: And that would be bad. Can we get off this thing now? Please? Tim and Moby are sitting on the pterosaur skeleton hanging from the ceiling at the museum. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts